The Seattle Mariners have several intriguing prospects worth watching this spring. Among the pitchers, Kade Anderson appears to be the most likely candidate for a call-up this season after delivering an impressive performance in his spring training debut. Another arm drawing attention is Ryan Sloan. While he is still further away from the major leagues, he made a strong impression in his lone outing so far this spring. However, the young pitcher still has areas of his game he is trying to refine.
One of Sloan’s current priorities is developing a sinker to pair with his four-seam fastball, which has shown some flaws despite its eye-catching velocity. On the surface, his fastball looks like it could already be a big-league weapon. Scouts have clocked it sitting around 95–96 mph and occasionally touching the upper 90s. But modern pitching analysis emphasizes that induced vertical break can be just as important as raw speed when evaluating how effective a fastball truly is.
Up to this point, Sloan’s fastball has been fairly flat, which has limited its ability to generate swings and misses. Last season his whiff rate was only 20.5 percent, and in his spring training appearance the induced vertical break on his four-seamer measured just 15.3 inches. That lack of movement contributed to hitters posting an .880 OPS against the pitch in the minors last year.
Justin Toole, the Mariners’ Director of Player Development, recently discussed the organization’s approach to helping Sloan take the next step. A key part of that plan is introducing a sinker into his pitch mix.
Toole noted that as Sloan continues to get stronger, the velocity on his four-seam fastball could climb slightly, which may also improve its shape and overall effectiveness. He added that giving Sloan a two-seam fastball has already been encouraging, as the young pitcher has shown confidence throwing it even against top major league hitters during spring sessions in front of fans and teammates.
Adding a pitch that moves toward the arm side complements Sloan’s existing kick-change and helps round out his arsenal. For pitchers who have velocity but lack the ideal fastball shape to consistently produce strikeouts, generating ground balls can often be a more efficient path to recording outs.
The adjustment also highlights the Mariners’ proactive approach to pitching development. Rather than assuming a pitcher with Sloan’s 6-foot-5 frame and raw talent will eventually figure things out on his own, Seattle’s development staff is already working to address potential weaknesses early.
Seattle’s farm system continues to produce intriguing talent, and Sloan could be one of the next prospects to emerge. Although the 20-year-old is not expected to reach the majors until around 2028, the right adjustments could accelerate his path and make him a future piece of the Mariners’ pitching staff sooner than many anticipate.